Browsing by Author "Amara, Khira"
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- Chemical composition and evaluation of antioxidant, antimicrobial and antiproliferative activities of Tuber and Terfezia trufflesPublication . Tejedor-Calvo, Eva; Amara, Khira; Reis, Filipa S.; Barros, Lillian; Martins, Anabela; Calhelha, Ricardo C.; Venturini, Maria Eugenia; Blanco, Domingo; Redondo, Diego; Marco, Pedro; Ferreira, Isabel C.F.R.Ten truffle species of Tuber and Terfezia genera were chemical characterized, assessing their proximate composition, individual nutrient compounds and some bioactive molecules. The bioactive properties of these species were also evaluated, namely their antioxidant, antimicrobial and cytotoxic potential. Carbohydrates were the main macronutrients present in truffles, followed by proteins. Furthermore, the levels of polyunsaturated fatty acids (PUFA), subsequently presented as a percentage, were higher in truffles (38.2–79.3%) except in Tuber magnatum and Terfezia arenaria, which have a more saturated fatty acids (SFA) profile (70.7% and 53.7%, respectively). Comparing the species, T. magnatum revealed the highest levels of total phenolic compounds (TPC) (290 mg GAE/100 g truffle), as also the best results in the four methods used to evaluate the antioxidant activity. On the other hand, only five extracts obtained from some studied truffle species (Terfezia magnusii, Tuber aes-tivum, Tuber gennadii, and Tuber melanosporum) showed a slight inhibition of microbial growth, tested against different bacteria. Terfezia and T. gennadii extracts, showed potential to inhibit the cellular growth of NCI-H460, HeLa, HepG2, and MCF-7 cell lines (GI50 concentrations range: 19–78, 33–301, 83–321 and 102–321 μg/mL, respectively), indicating anti-proliferative activity. Nevertheless, T. arenaria revealed some potential hepato-toxicity, inhibiting the growth of PLP2 cells (GI50 concentration of 220 μg/mL), a primary cell culture obtained from porcine liver.
- In vitro production of Ganoderma lucidum mycelium from northeast Portugal: The antioxidant potential of tocopherols extract in the preservation of natural yogurtPublication . Amara, Khira; Martins, Anabela; Ferreira, Isabel C.F.R.; Skhiri, FethiaThe increase in public awareness for the direct relationship between diet and health has led to concerns related to the use of commercial food additives, promoting the search for natural alternatives. Thus, natural antioxidants are among the most searched compounds nowadays, due to the issues related with the oxidative stress and its harmful effects on both food quality and human health. Tocopherols are among the most well-known and interesting natural antioxidants because its use as a food additive has multiple benefits. These are encompassed by the designation of vitamin E, which is an essential and extremely important micronutrient for human health that should be provided by the diet, being a strong wall against oxidation, especially in cooperation with vitamin C. The use of natural tocopherols at an industrial level depends on the sustained production, hence the importance and choice of the in vitro culture as an alternative to their production. The in vitro production of natural compounds allows a continuous year round availability of the demanded products in an independent way of environmental conditions and without ecological issues. In recent years, mushrooms became more and more value and exploited due to their richness on valuable compounds with biotechnological interest and to their easier and faster in vitro production compared to plants. Moreover, the in vitro production of mushrooms mycelium has been explored to improve the synthesis of antioxidants, namely tocopherols. The present work aims to evaluate the tocopherols content of the well-known medicinal mushroom Ganoderma lucidum (Curtis) P. Karst from the Northeast of Portugal, produced by in vitro culture, and comparing with its fruiting body. The tocopherol levels were determined by chromatographic techniques, namely by high performance liquid chromatography coupled to a fluorescence detector (HPLC-fluorescence). Afterwards, a tocopherol rich extract from the mycelium was incorporated in natural yogurts, and the antioxidant potential of the extract (before incorporation) and yogurts (after incorporation) was assessed, in order to study its potential as a food additive. The antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the reducing power assays. Moreover, the effectiveness of the tocopherol rich extract as a food Abstract xi additive was evaluated for the maintenance of the nutritional properties of the studied food matrix. These studies were carried out comparing the nutritional parameters of four yogurt formulations: i) control (yogurt without any type fortifying agent); ii) yogurt with potassium sorbate - E202; iii) yogurt with α-tocopherol - E307; and iv) yogurt with G. lucidum mycelium tocopherol enriched extract. Overall, with regard to the in vitro culture, G. lucidum mycelium did not show significant differences in radial growth between the two used media. The chemical analysis showed that the in vitro produced mycelium of G. lucidum was particularly rich in -tocopherol (362±7 μg/g extract) and β-tocopherol (272±8 μg/g extract), among the total tocopherols content 717±12 μg tocopherols/g extract with relevant differences in comparison to the corresponding fruiting body. Besides, G. lucidum mycelium showed good results in the DPPH radical scavenging activity assay (EC50 = 10.4±0.2 mg/mL), but especially good in the reducing power assay (EC50 = 0.32±0.01 mg/mL). While, different results were registered in the tested yogurt formulations with the highest antioxidant activities observed in yogurts incorporated with α-tocopherol and G. lucidum extract. Besides, no particularly significant differences were observed among 0 and 7 days, especially in yogurts incorporated with tocopherol enriched extract obtained from G. lucidum mycelium. The evaluation of the interaction between the yogurts formulations (YF) and the storage time (ST) on the nutritional composition of yogurts, showed a significant impact on fat, protein and lactose, indicating that the ST influenced these parameters differently for each YF. Furthermore, the effect of YF was only significant for fat, protein, carbohydrates and lactose, resulting that the statistical classification could only be indicated for carbohydrates, which reached maximum values in yogurts prepared with potassium sorbate (5.9±0.2 g/100 g). Also, significant changes in the contents of fat, protein and lactose were registered due to the ST with higher values for fat and lactose in yogurts stored during 7 days, while the protein content did not showed any identifiable tendency. Furthermore, the fatty acids profile showed that the changes induced by ST vary according to YF in most cases and that ST did not induce significant changes in the fatty acids profile, with exception for C4:0, C8:0 and C18:1n9. Abstract xii According to the Linear Discriminant Analysis (LDA), it was possible to identify the most distinctive parameters of each YF, allowing to choose the functionalizing agent (potassium sorbate, α-tocopherol or the enriched extract in tocopherols obtained from G. lucidum mycelium), according to a specific objective (in this case preservative effect). Considering the values of the antioxidant activity, it can be concluded that the yogurt incorporated with α-tocopherol or extract enriched in tocopherols obtained from the mycelium of G. lucidum, presented a greater preservation potential. Overall, the mycelium of G. lucidum might certainly be considered as a potential source of tocopherols to be employed as food lipophilic antioxidants.
- Incorporation of tocopherol-rich extracts from mushroom mycelia into yogurtPublication . Bouzgarrou, Chaima; Amara, Khira; Reis, Filipa S.; Barreira, João C.M.; Skhiri, Fethia; Chatti, Noureddine; Martins, Anabela; Barros, Lillian; Ferreira, Isabel C.F.R.Consumers are well-informed about food additives and it is likely that they prefer natural additives over their synthetic analogues. Antioxidants represent a major class of food preservatives, among which tocopherols stand out as one of the most important examples. Interestingly, these compounds are present in relevant amounts in the mycelia of in vitro cultured mushrooms. Accordingly, the mycelia from Ganoderma lucidum, Pleurotus ostreatus and Pleurotus eryngii were used as alternative sources of tocopherols. These extracts were incorporated into different yogurt formulations, which were further compared among each other and with yogurts containing commercial α-tocopherol (E307), regarding their nutritional parameters, fatty acid profile and antioxidant activity. The proposed approach was validated as an effective functionalization strategy, particularly in the case of the G. lucidum mycelium, which showed the highest antioxidant potential, most likely as a result of its tocopherol profile. Furthermore, yogurts prepared with each mycelium extract allowed maintaining the nutritional properties observed in the “blank” yogurt formulation.
- Nutritional values, chemical characterization and cytotoxicity in human tumor cell lines of desert trufflesPublication . Amara, Khira; Reis, Filipa S.; Barros, Lillian; Skhiri, Fethia; Martins, Anabela; Ferreira, Isabel C.F.R.Mushrooms are widely appreciated for their nutritional value, as well as for their health promoting properties [1,2]. Due to their proven bioactive potential, their application in food (e.g., incorporation of mushroom extracts in food products and functional foods) and pharmaceutical (e.g., nutraceuticals and food supplements incorporating mushrooms) industries, or the cosmetics industry (e.g., antiaging products) has been explored [3-5]. The present work intends to determine the chemical and nutritional composition, as also to evaluate the cytotoxicity of samples from a mushroom genus commonly known as desert truffles – Terfezia. To this end, three different species were studied, namely Terfezia arenaria (Moris) Trappe, Terfezia magnusii Mattir., and Terfezia leptoderma Tul. The nutritional value (protein, fat, carbohydrates and energetic value) of the species was evaluated following standard procedures, and their content in hydrophilic compounds (e.g., soluble sugars, phenolic and other organic acids) and lipophilic compounds (e.g., fatty acids and tocopherols) was assessed by chromatographic techniques (High Performance Liquid Chromatography and Gas Chromatography). The cytotoxic potential of the samples was also evaluated, testing the mushroom species against a panel of human tumor cell lines (MCF7- breast carcinoma, HeLa- cervical carcinoma, NCI-H460- non-small cell lung carcinoma and HepG2- hepatocellular carcinoma) and against porcine liver primary cells (PLP2). All samples proved to have high contents in carbohydrates and proteins, being low fat products. Mannitol and trehalose were the main sugars found, being also present bioactive phenolic acids. Among the lipophilic compounds, linoleic, oleic and plamitic acids were the major fatty acids present in the samples, together with different tocopherol vitamers. None of the samples showed cytotoxicity against non-tumor cells being in course the bioassays with human tumor cell lines. Overall, desert truffles proved to be highly nutritional species with bioactive compounds and potential to be used as cytotoxic agents.
- Utilização do micélio de Ganoderma lucidum para obtenção de extratos ricos em tocoferóis para aplicação como antioxidantes alimentaresPublication . Reis, Filipa S.; Caleja, Cristina; Amara, Khira; Barreira, João C.M.; Martins, Anabela; Skhiri, Fethia; Barros, Lillian; Ferreira, Isabel C.F.R.Atualmente, os consumidores estão mais bem informados acerca dos aditivos presentes nas matrizes alimentares e, cada vez mais, se encontra uma preferência por alternativas naturais relativamente aos análogos artificiais [1]. Os cogumelos sao consumidos em todo o mundo e são considerados alimentos funcionais devido a sua constituição química, rica em compostos bioativos, nomeadamente em tocofer6is [2]. Os tocofer6is sao poderosos antioxidantes que podem ser explorados coma aditivos naturais de alimentos, de forma a substituir os análogos artificiais utilizados extensivamente. Com estes aspetos em mente, e com a evidencia de que a cultura in vitro de micélio de cogumelos promove a produção de tocoferóis, o objetivo deste trabalho foi incorporar em iogurte natural, um extrato rico em tocofer6is obtido a partir da espécie Ganoderma lucidum (Curtis) P. Karst. Os níveis de tocofer6is foram determinados por técnicas cromatográficas, nomeadamente por cromatografia liquida de alta eficiência acoplada a um detetor de fluorescência (HPLC fluorescência). Posteriormente, o extrato enriquecido em tocofer6is obtido do micélio foi incorporado em iogurte natural avaliando-se o potencial antioxidante do extrato (antes da incorporação) e dos iogurtes (apóss incorporação), a fim de estudar o seu potencial como antioxidante alimentar. Foram avaliadas a atividade captadora de radicais 2,2-difenil-1-picrilhidrazilo (DPPH) e o poder redutor. Foi também estudada a eficácia do extrato rico em tocoferóis coma antioxidante alimentar, na preservação das propriedades nutricionais da matriz alimentar estudada. Estes estudos foram realizados comparando os parâmetros nutricionais de quatro formulações de iogurtes: i) iogurte controlo; ii) iogurte com sorbato de potássio E202; iii) iogurte com α-tocoferol - E307; e iv) iogurte com extrato rico em tocoferóis obtido do micélio de G. lucidum. A analise química mostrou que o micélio produzido in vitro e particularmente rico em α-tocoferol (272 j..lg/g de extrato) e 6-tocoferol (362 j..lg/g de extrato), apresentando um total de 717 j..lg de tocofer6is/g extrato. 0 micélio apresentou capacidade de captação de radicais DPPH (EC50 = 10,4 mg/ml), demonstrando ainda maior poder redutor (EC50 = 0,32 mg/ml). As formulações de iogurte com maior atividade antioxidante pertenceram ao grupo incorporado com o aditivo atocoferol e com o extrato rico em tocofer6is obtido do micélio de G. lucidum . Contudo, não foram observadas diferenças significativas entre 0 e 7 dias, particularmente no iogurte incorporado com extrato de micélio de G. lucidum. Atendendo aos valores da atividade antioxidante, pode concluir-se que os iogurtes incorporados com α-tocoferol ou com o extrato rico em tocofer6is obtido a partir do micélio de G. lucidum, foram os mais eficazes. Em geral, o micélio de G. lucidum pode, de facto, ser considerado coma uma potencial fonte de tocoferóis que podem ser introduzidos em alimentos como antioxidantes lipofflicos.